I know people here just can't live without pictures, so here is what I have. When I started my original tank I needed a place to put the equipment and the only place I could think of was in the "crawl space", so here is what I did sorry the picture are not that good.
This is what it looked like before I started
Here is after many, many, many hours of digging
and
I put a drain in the center of the floor and once the floor is poured I will have a 7' ceiling